A mechanism for migrating bacterial populations to non-genetically adapt to new environments

Populations of bacteria can rapidly expand into new territory by consuming and chasing an attractant cue in the environment, but the consequences of non-genetic diversity for this process are unknown. Through theory and simulations, we predict that expanding populations non-genetically adapt their phenotype compositions to migrate effectively through multiple physical environments. Swimming phenotypes in the migrating group are spatially sorted by their chemotactic performance, but the mapping from phenotype to performance depends on the environment. Therefore, phenotypes that perform poorly localize to the back of the group and selectively fall behind. Thus, the group composition dynamically enriches for high performers, enhancing migration speed and overall growth. Furthermore, non-genetic inheritance controls a trade-off between large composition shifts and slow responsiveness to new environments. These results demonstrate that phenotypic diversity and collective behavior can synergize to produce emergent functionalities. Furthermore, non-genetic inheritance may generically enable bacterial populations to transiently adapt without mutations, emphasizing that genotype-to-phenotype mappings are context-dependent.